Test whether undirected edges are part of a graph:

Test directed edges:

EdgeQ works with undirected graphs:

Directed graphs:

Multigraphs:

Mixed graphs:

EdgeQ returns False for items that are not edge expressions:

Rules can be used to test for directed edges:

When g is not a graph, EdgeQ[g,e] evaluates to False:

Verify that g is not a graph using GraphQ:

EdgeQ works with large graphs:

Compare performance with a test based on EdgeList:

Test whether 5 is adjacent to 1:

Check input to a function:

Take correct action depending on whether an item is an edge or a vertex:

Act on an edge:

Act on a vertex:

EdgeQ[g,uv] is equivalent to MemberQ[EdgeList[g],uv]:

The performance of EdgeQ is typically higher:

EdgeQ[g,uv] is equivalent to MemberQ[EdgeList[g],uv|vu]:

The performance of EdgeQ is typically higher:

Use EdgeIndex to find the position of an edge in EdgeList[g]:

EdgeIndex is typically faster than Position:

Use VertexQ to test whether a vertex is part of a graph:

Some edges do not seem to be recognized:

Membership is tested using SameQ rather than Equal:

By using identical expressions it can still be tested: